A large millstone used in Mexico for the production of tequila and mezcal.
After cooking the piña of the agave, liquid must be separated from the fibers, by crushing the pulp. While industrial scale production uses mechanical metal grinders, tequila producers who capitalize on "authentic" production methods use a traditional large crushing wheel carved from tezontle, a volcanic rock. Weighing up to two tons, the tahona was traditionally moved by mules or men. Nowadays a motor (or in some artisanal producers, donkeys) drive the wheel.
Sources:
Camper English. "Bay Area distillers play around with Tequila." San Francisco Chronicle. February 1, 2009.
Tim Leffel. Ten Years to Tequila: On the Agave Trail in Mexico." Perceptive Travel. March 2007. http://www.perceptivetravel.com/issues/0307/leffel.html (February 2, 2009)
Pernod Ricard USA Press Release. "New Tahona Handcrafted Tequila Introduced to US Market" August 1, 2005. http://www.beststuff.com/fromthewire/new-tahona-handcrafted-tequila-introduced-to-us-market.html (February 2, 2009)